U.S. Pat. No. 4,159,158 describes an electrical contact terminal which comprises an elongated section of sheet metal which is folded, with respect to transverse fold lines, to provide side-by-side coextensive arms. The arms have convergent portions and have opposed contact zones on the convergent portions so that a post or blade can be inserted between the arms and the arms will establish electrical contact with the post or blade. The terminal of the above identified U.S. patent is connected to a wire by means of a wire-receiving slot which extends into the folded portion of the terminal.
Terminals of the general type shown in U.S. Pat. No. 4,159,158 are widely used in many different forms. The convergent arms between which the complementary terminal is received are easily produced in sheet metal terminals and under many circumstances will provide adequate contact pressure for a stable electrical connection. The contact pressure which is developed in terminals of this type is largely dependent upon the dimensions of the arms and the physical properties of the material from which the terminal is produced. If the arms are relatively long, it is necessary to use fairly thick material having good spring characteristics to develop an adequate contact pressure. Under some circumstances, the spring arms can be supported by the walls of the housing in which the terminal is contained for the purpose of increasing the contact pressure but this expedient is not always satisfactory for the reason that the housing is usually of a thermoplastic material and it may relax after the passage of time with a resulting relaxation of the contact force. The present invention, in accordance with one aspect thereof, is directed to the achievement of a stamped and formed contact terminal having side-by-side arms and having a bracing means extending between the arms which permits control of the contact force developed by the spring arms.
In accordance with a further aspect thereof, the invention is directed to the achievement of a terminal having spring arms which have contact zones adjacent to their ends, the contact zones being preloaded against each other. When a terminal of this type is plated with a conductive corrosion resistant material, such as gold or tin, it is essential that the plating cover the contact zones, since these zones are the most critical parts of the terminal. If the terminal is plated after complete forming thereof, the plating metal will obviously not be deposited on contact zones which are against each other. The invention is further directed to the manufacture of terminals having their contact zones against each other and having plating metal completely covering these contact zones.
A contact terminal in accordance with the invention comprises an elongated section of conductive sheet metal which is folded about medial transversely extending fold lines to form two side-by-side coextensive arms. A wire connecting portion is provided at the fold in the form of wire-receiving slots into which the wire is inserted. The arms have parallel portions extending from the fold and the arms have convergent portions extending from the ends of the parallel portions. The convergent portions extend to contact zones on the opposed surfaces of the arms. The contact zones are against each other and are preloaded, that is, resiliently stressed so that a minimum contact force is established when a blade or post is inserted between the arms. A brace is provided which extends between the arms at a location spaced from the contact zones. This brace restrains the arms against outward movement so that when the blade is inserted between the contact zones, the portions of the arms which extend from the brace to the contact zones function as cantilever beams. The stresses developed in these beams upon insertion of the blade further contribute to the contact force which is developed when the blade is fully inserted.
Terminals in accordance with the invention are manufactured in strip form with each terminal extending from a continuous carrier strip. When the terminals are in strip form, the contact zones are not against each other and the brace is disengaged so that the terminals can be plated and plating metal will be deposited on the contact zones. When the individual terminals are removed from the strip and inserted into a connector housing, the brace is engaged and the arms are flexed so that the contact zones are against each other and preloaded against each other.